Various types of phosphors are known that emit light in a range from the ultraviolet range on the longer wavelength side to the visible light range on the shorter wavelength side. However, a phosphor is not known that has excellent light resistance, and effectively emits reddish orange light. As a phosphor that emits green light, a (Sr, Ca)S:Eu group phosphor is mainly used. However, the (Sr, Ca)S:Eu group phosphor has poor weather resistance and low light emission efficiency.
As a silicate yellow group phosphor, which absorbs blue light that is emitted by a blue light-emitting diode and emits yellow range light different from the (Sr, Ca)S:Eu group phosphor, a silicate phosphor is known that is represented by the chemical formula of Sr2SiO4:Eu (see Patent Document 1, for example).
Patent Document 1: Japanese Patent Laid-Open Publication No. 2005-277441